The present invention relates to a latch system, in a particular a latch system for a vehicle door, such as a car door.
European patent application no. EP 01310100 shows a known latch arrangement (see FIG. 20 of the present case). The latch arrangement includes a latch chassis 1 on which is rotatably mounted a lever 2 which operates a link 3, which in turn moves a pin 4 to release the latch. Movement of the link 3 is controlled by a lever 5 and a link 6. The position of the lever 5 is controlled either by an electromagnet 7 or by a permanent magnet 8. Springs 9A and 9B control the position of various components during operation.
One of the embodiments shown in European patent application no. EP 01310124 shows a similar arrangement.
In both cases, the lever 5 can be prevented from moving in one of two ways: either by powering the electromagnet 7 or by positioning an end of the permanent magnet 8 underneath an end of the lever 5. When the electromagnet 7 is powered, it consumes power, and therefore the electromagnet 7 is typically only used to lock the vehicle when the associated engine is running and hence the vehicle's battery is not discharged.
When the permanent magnet 8 is used to hold the position of the lever 5, a key is required to disengage the permanent magnet 8 from the lever 5, or alternatively the electromagnet 7 can be momentarily powered so as to move the permanent magnet 8 by virtue of a magnetic field generated by the electromagnet 7. Typically, the permanent magnet 8 is used to lock the vehicle when the driver is absent from the vehicle.
However, there are occasions when a driver or other vehicle occupant may wish to remain in the vehicle (perhaps while taking a rest on a long journey), but nevertheless have the vehicle doors locked. Under these circumstances, the vehicle engine will not be running and hence locking the vehicle using the electromagnet 7 would potentially drain the vehicle's battery. On the other hand, if the vehicle is locked by using the permanent magnet 8 and then an electrical failure occurred, it is not possible to unlock the vehicle using the electromagnet 7 to move the permanent magnet 8. Using a key to move the permanent magnet 8 would be awkward for an occupant of the vehicle since the key hole would be on the outside of the vehicle.